Note(s): Variability in the duration of the free-swimming period of lecithotrophic larvae of the demosponge Sigmadocia caerulea (Hechtel, 1965) was assessed in the laboratory in the absence of metamorphic inducers and inhibitors. The free-swimming period in three clutches of larvae ranged from 8 to 70 h and the cumulative settlement curve was sigmoid, with settlement peaking between 20 and 28 h after release. There were significant differences among clutches in the time to reach 50% settlement. Within each clutch, small percentages of larvae (